Inner tube.



C.' L. WITSAIVIAN.

INNERTUB. y APPLICATION FILED MAR'. 5. 1915. 4

Pawnf Apr. 16, 1.918.

Ehmeutur CLEMENT Ai.. WITsAMAfN, or' S1JMMI'-L1A counrronrdfnssrenon To THE FIRESTONE TIRE' l I y j vttarisruaz.contrario?, or 'nunon H10,- nfconromfrron oF oHIo.

a Befit'. own that I, CLEMENT L. WITsA- MAN-a citizen of the United States, resld-v inginthe county "of Summit and State of Ohio,'h ave .invented certain new and -useful Improvements lin! .Innerx ubes, of .whlch the following aispecilication. l

`The object of'my inventiolrhas been to make'an' inner tube for tires which willbe' as .nearly-puncture-proof and self-heating as it is possibleto make it .without deprlvinglthetube of auf' yresiliencyand without introducing a text el material into-1 the t ube. Myginvention also has for one of its ob] ects themethod of making-the tube. f

,.l .Iti's well known thatrubber under compression possesses? the propert "of' closing .any holeswliich maybe formed7 m1 1t4 by expansion ofthe rubber. Itis also common 20 knowledge that; the red .,rubber, -orl rubber containing antimony compounds and enough lsulfur tochemically'A combine with the rubberbut not enough to' leaveany free sulfur. after curing, commonly known as tube stock "is highly resilient and will keep .its resiliency fora lon period, not being sub` ject to kfurther vu canization during .use .f It is also -well known that gray rubber, commonlyknown as ltread stock consists of rubber heavily. compounded without any antimony compounds, is, tough, not jeaslly Y puncturedv `and whenv under compression 'possessestoa'high degree the property of :closing 'J up any, fpunctures" formed therein.

With .these "facts inmind it has beenl my purpose toconstruct a puncture-proof and self-healing' tube bymakng use of the properties of the two kinds of stock mentioned, but Ido not wishto be limited to I were.

s 4Speciication otIetters Patent. 'Patented A'ppuatibn mea March 5, 1915. `serial No; 12,286.

.. pQSiuonfit-.naprally assumes whe ffromthe pole. l u .I

through the 'tough A the tube, the puncture caused; thereby-Will Aer. 16,1918.

draw'al of thev ypuncturing element, owing to the compression under .rubber `isv held. y

In order .to .carry out whichV the tough ing same which is illustra-ted ther'accomnumeralsy refer vto `like parts, andjinwhich Figurefilf' 1s la cross sectionfof my y tube prior tofitsfflgemoval from4 aupolefon .which appeasfwhell inflated in use. v In malnng my tube the operatorwraps the tread of the tire in use'and cover about' l Fig. 3is a cross section ofi-my v tube ask'it one-half of the circumference-of the cross-f.

section of thel tube. Over this layer he then places a vslngle'ply of tube stock v3. IThe completed tube is'- then removed from the mandreland blown on toa curing pole on whichit is cured.- l.Alfter curing the tube is removed from the pole by turninginside out, or peeling `in stocking fashion. This .places the .two ply layer of tube-stock on the outslde of the tube and as :itisfsmalle'r in circumference its tendency lto contract to original size and its resilience places the layer of-- tread stock under a certain degree of compression. This gives the layer of tread stock the puncture healing propertyl which is also increased because of thefact that a tougher and less resilient rubber having been forced in one shape'by curing will have a greater ltendency to assume that shape if forced in to any other' shape than a more resilient softer tube. This is illustrated in Fig.' 2 of drawing in which is loo " inflating the tire the tread portion is comfpelled to take a reversed curvature from thatwhich it is its' natural tendency to asf sume`, which places the tread stock under '5 additional compression.' K j It is, therefore,l evident that the compression in t'h'e'tread stock is caused by two :tac-

t'ors. j First, the' 'contraction' of' theV outer Slayer of very resilient rubber and, secondyby 1.0 the internal compression in the tread stock l tube its puncture.healing'property to such ailarge'eitent, and the selection ofthe diftering in t-he compression of the tread stock is believedfto be one ot' the principalfea- `ttlres of myl invention.l To 'get the greatest internal compression'in the rubber. due to `anyaltering of shape andthe tendency to return to the original shape, I use atou'gh,v

slightly resilientrubber, but tobbtain the greatest external compression "I- use. a highly ,resilientrubber such as thetu'bestock men- "tioned Thefinner'tube stock used is 'p ecu# V-liarly suited to .the work required of it asit .'does'h'notj fatigue easily, that is,l itsy elast` ,tendency in all tubes to 'slowly increasein cross section during use, but this tendency 'l is less in tube stocks of'highresiliency. In

use lmy' tube has vshown about the same in- 4 :crease in size that is shownina; tube made wholly' ofthe more 'resilient tube stock.. lt 40 v of the tread stock this tube would show a, greater permanent increase than one of tube stock alone, but the result demonstrated thatv the outer layer o f tube stock restrained thev '45 less resilient tread stock-from permanently increasln-g in size during use, more rapidly than itself. v

It should, also .be noted that the presence 'due toits tendency to assume av reverse cur-4 vatu'refrom thatv which-it is given when 11i'. Suse.' lt isthesetwo factors that give my' ferent :stocks to obtain the't'wo faetorsenl ticity 'orfcome back is little affected by a4 tenslo'n strain of anyconsiderable duration. For this reason the .compression vdue to thecontraction xof the y outer layer` is heldl throughout the life of the tube. There is a would be expectedthat due to the presence "tubesztq use either -afcomplete layer. or a. Aistrip ofiabric on the inside `oii atube and 'ressens 4 containanyftabric. Ylihis put'sia strain en.v the points about the tube wherev the abrid. A ends, and tubes of this type arevliableito rup-` f f ture aboutthe edges 'of the lfab'ric., I .also

am aware 'that it has been pro' osped'to ce-- 70 y ment one layer of rubber to anot er layer of rubberwhih-fis stretched out'- ofl its, norma1 state, l'thatis depending upon the return of lthe stretchedrnbber to normal lto place .the

ltheriayer undera'compression. ",lhiahov 75 ever, has thevdjeadv'antage that anyl puncture' occurring in the-stretched layer will have a tendency to spread. .l I overcome this 'disadvantage in my tube byl` reason of thejfactl that in use the external layer is very`nearly in its'normal state. `In-all tubes'which rely on compression to obtaina puncture healing property and which, are extensible in their compressed areas,- the compressionl is neu'- tralized-v by the' extension due toA inflation. 85 This is particularly true 'in tubes which have soft-rubberinv the compressed state, as soft .rubber will? require lessfforce tocompress it to a given volume and its lossof compression upon increase in size at inflation will be v 910 more marked. In my tube, however, the i minimum-V loss of compression is` present which is compatible with a tube resilient throughout. This is owing to thecomparal tive inexten'sibility of the compressed layer. 95 Details 'of my invention as set forth might be changed without departing fromthe sub stance thereof and without sacrificing any of its advantages. L f What I claim is: 'i 10@ 1. puncture healing tube consisting of a compound vstructure of di'erent.: rubber stocks, thelstock of the outer layer having' greater resilience than that `of -the ;inner` i layer; the puncture healingzproperty-being imparted by compression in the less resilienty eyee r 1 `2. A tube consistin `of a compound structureof layers "of rub er stocks of di'erent degrees of resiliency, theless resilient stock 11e being held under compression by the more resilient, 'the tube being expansible at 'all'.v

points.v y f 3. A tube consisting of a compound struce ture of layersof rubber" stocks of dinerentlle 'v degrees of resiliency, the lessresilient stock being located between two layers of the more i Y- resilient stock and held-under compression `1 by the more resilient stock, andby ination 'f ian ont the tube.v 1 .l l

4 tube consistinfof al'cenipound struc-,l ture 4ot layers or ruber `stocks of direm,

'degrees o i.-ret'liency, the less resilient-stock'v beingth'ickened-at the wearing' point, and located betweenka thick outer layer and a- Z thin inner layer et the more resilient stoel;l i

5. A tube compos-ed of two layers si? dif! ferent rubber steclrs, the outer layer being l the in i d meme@ compression by the outeiT laye@ an by in layer, anni by its tenc'ieny to assume a ref atio. b d f l d verse curvature from that given it in uses 6. tu e compose o tWo ayers o i ferent rubber stocks, the outei` layer being CLEMENT L' WTSAMAN 5 more resilient and the inner layer being Witnesses:

tougher, the inner-layer being held under J. J. Sm? compression by the contraction ot' the outer A.' L., Emi, 

